This invention relates to a speaker driving circuit and particularly to a circuit for providing, from an audio speaker, sounds by which operations of a key-board, various switches and the like are confirmed, for example, in a PLL synthesized radio receiver with the key-board for data entry.
In such receiver, when a key push button on the key-board is depressed, a sound is generated from the audio speaker equipped on the receiver housing, whereby the depression can be confirmed.
Prior art circuits for providing such operation confirming sounds have used an audio amplifier which is in active state, and, therefor during the operation mode of muting, squelching or the like wherein the audio amplifier is made ineffective, the operation confirming sounds could not be generated.
The main object of the invention is to provide the operation confirming sounds even though the audio amplifier is ineffective. Other objects of the invention will be clear from the detailed explanation of the invention .